Now, from Chiang Rai Airport near Phayao (though it takes nearly two hours to get there), I'm heading back to Bangkok for now. This trip involved quite a few rushed transfers. However, my ally Prof. S seems quite pleased with the formalities at Phayao Lake and the warm hospitality from the university.

Unlike the outbound trip, we're returning to Bangkok from Chiang Rai Airport. While LCC flights don't usually include meals, I was given the very front seat and even served a meal. This was thanks to the university's kindness. I can only express my gratitude. This grilled mackerel with teriyaki sauce was delicious.

Well then, I'm back at Bangkok's second airport, Don Mueang. After a few hours' rest here, I'll head to Mukdahan next. But instead of the usual Ubon Ratchathani, this time I'm flying to another airport called Nakhon Phanom. However, a major problem arose here. My Priority Pass card, which I always use for lounge access, wasn't recognized at any lounge. My plan to have lunch and rest fell through. This was actually because I had forgotten to register for the digital membership card, but at the time, I had no clue about that. My mind was completely occupied with how to contact the card company. In the end, while Mr. S enjoyed the lounge, I ended up with a meager lunch of just a McDonald's Filet-O-Fish.

Nakhon Phanom is a border town along the Mekong River, just north of Mukdahan, and this is my first time here. The horizon was unusually beautiful, with gaps in the gray clouds covering the land. When I asked Mr. S about it, he said it was likely the boundary of an inversion layer. This area is the Khorat Plateau, a vast plain.

You can see slightly hilly terrain. Typical kesta landforms are visible. What's interesting here is that these uplifted strata are actually Early Cretaceous to Late Jurassic layers beneath the plain's strata. This inverts the relationship between topography and stratigraphic age because the strata dip slightly toward the hills. This is a geological feature commonly observed on continents. I'll explain this during the geological field trip at the high school in Roi Et, our next destination.

Well, when the plane landed at Nakhon Phanom Airport and I boarded the bus from the remote stand to the terminal building, I happened to bump right into this student's family sitting next to me. Would you believe it? I had given a special lecture at PCSHS Mukdahan last year, and she remembered it and came over to say hello. It was a surprise, even if it was a coincidence. Her parents were also very refined people. I was truly amazed. They said they were in Bangkok for shopping or something and were heading back to school.

Now, the next day marks the first day of the seismometer-building workshop at Mukdahan School. All the parts have been prepared for the participants who have already rushed over from twelve nearby high schools. This workshop involves assembling these components into fully functional seismometers within three days.

Preparing for twelve schools is no small task. I hear Mr. Pao, the teacher in charge of practical training at this high school, did almost all of this preparation by himself over the course of a month. I take my hat off to his effort.

Assembly begins with tapping the screw holes. This is likely the students' first time doing this task, and though they're a bit hesitant, they skillfully get the job done. Naturally, things don't always go smoothly, but in those cases, we've prepared nuts in advance to handle the situation.

Assembling the main body involves bonding acrylic plates, pre-cut by laser cutter, using acrylic adhesive. With a considerable number of parts, this too is challenging until you get the hang of it. Initially, we applied the adhesive with a brush, but it didn't work well. After my suggestion to switch to a syringe, the adhesive spread evenly, resulting in transparent bonding surfaces. A small but effective tweak.

Not only the students, but the accompanying teacher is also trying their hand at tapping. This teacher seems to specialize in physics. They also handled the soldering with skill.

For this workshop, daily Japanese-style boxed lunches like this were prepared for me and observer Prof.S. They even included miso soup, and it was incredibly delicious and much appreciated. We're grateful to the high school.

In the afternoon, we soldered electronic circuit boards. This wasn't part of any pre-planned schedule either; we came up with the task assignments on the spot that day. After all, it was our first time, so it wasn't something we could plan out perfectly from the start. It was mostly improvisation every day. The explanations were provided by Mr. M, the IT specialist. He apparently used to work in development at an electronics manufacturing company. Actually, he had prepared 12 spare boards in advance, just in case any students messed up their soldering. But the students' soldering skills were quite good, and only a few groups needed to swap out their boards.

During assembly, we encountered design flaws in the board supporting the pendulum's pivot point and had to urgently remake the part. This is Professor P, the instructor in charge of the physics experiments. His machining skills and technical expertise are second nature to him; it's no exaggeration to say this workshop wouldn't have been possible without him.

Now for the soldering. Many students were doing this for the first time and seemed nervous, but with Mr. M's precise guidance, their skills gradually improved. You can see the masks and exhaust ducts—a precaution to avoid inhaling toxic lead fumes.

For the most critical part of the pendulum—the pivot tap—I demonstrated the method first, and then the science teachers who came to assist handled it.

That evening's dinner also featured a spread of luxurious Isan dishes (traditional cuisine from Thailand's northeast region). This one resembles a giant egg custard similar to chawanmushi.

The next day, students were cleaning the room early. This room at the venue is called the STEM Room, a facility found in all 12 PCSHS (Princess Chulabhorn Science High Schools). It's used for experiments and projects. In the back, there are six 3D printers, a large laser cutter, and various tools like a drill press. I doubt any Japanese high school has this level of equipment.

Mr. N, the physics teacher organizing this workshop, is explaining how to handle the coils. This time, I'm in an advisory role, asking the teachers at this school to run things as independently as possible. If this lab session goes well, I plan to ask him to present his research at the JpGU conference in Makuhari this May. Furthermore, I'm keen to hold this initiative in Japan next year. It would be great if someone stepped up to host it.

Finally, it's time to assemble the coils and magnetic circuits and mount them onto the Arduino boards. These are being attached to the acrylic plates that Professor P urgently made for us overnight after I asked him yesterday. Preparations were extremely tight—materials ordered online arrived late, and there was an ordering mistake for the copper pipes used for braking. Professor P's last-minute efforts saved the day.

Installing the coil. This part was also pre-made using a 3D printer or similar method. Since coil winding is very time-consuming, we purchased a new coil winder (the one in the lower left) and Professor P wound it himself. The coils arrived just before this workshop, so this part was also a bit of a rush job. The copper pipe for the pendulum's braking mechanism was pre-cut using a pipe cutter. The bottle contains acrylic adhesive.

We had to redesign the support pillar section, which meant urgently reprinting that part too. We're fully utilizing CAD and the laser cutter. Honestly, we should have done these tasks much earlier, but both myself and Professor N from this school were new to organizing such workshops, so preparations didn't progress smoothly. It ended up being three days of mostly improvising on the spot. Well, it's just like usual.

We're marking the centerline for attaching the pivot point parts that support the pendulum's rod with springs. Since this part affects the pendulum's stability, I advised them to proceed carefully.

At each school, the seismometers are gradually taking shape. Honestly, I thought completion was near at this point, but...

Now, with the magnet installed, Mr. M is checking whether the coil actually outputs a signal. That's where we ended work for the day. Well, for the second day, it went pretty much according to plan. Considering we're barely scraping by, things have gone surprisingly well so far (which means something might happen on the third and final day?).

With the second day completed without incident, we headed to the schoolyard for stargazing at S-san's strong request. Mr. N set up the telescope. S-san is struggling to take a photo of Jupiter. The man standing on the right in the back is Mr. N, the physics teacher who organized this seismometer workshop and has been helping us out.

Now, on the third day, after I explained the principles of seismometers and the mechanism of AD conversion up front, we proceeded to install the necessary software on the PCs each school had brought. Everything went very smoothly up to this point. However, at the end of the morning session, when we tried to connect all the circuits and view the signals on the PCs, none of the groups got any waveforms! This was a major crisis! To investigate the cause, we moved lunch forward and spent the lunch hour troubleshooting. Since the seismometer output seemed to be working, we suspected the amplifier? If the circuit board design was flawed, this workshop would be a complete failure. With time running short, we tried various approaches to find the cause. Checking with Mr. M, who was experienced with electronic boards, we suspected the cables were the culprit. We measured the cable resistance and confirmed it was the culprit with less than an hour left before the afternoon session started. We frantically removed the output socket and decided to connect using parallel wires instead of a shielded cable, making an emergency design change. Finally, we saw a glimmer of hope for restoring the signal and had a late lunch. But we never would have predicted that a cheap stereo cable was the cause!

Self-made materials used during the three-day training. They explain seismometer principles and electronic circuits. I briefly lectured on this content on the morning of the third day.

The amplifier board and the Arduino Uno-compatible board connected to it, completed through soldering by students and teachers who showed no signs of being beginners. The amplifier circuit PCB was ordered from a Chinese company last December. When the above signal didn't come out, my mind went blank for a moment, wondering if it was a design flaw in this board.

Thanks to the last-minute design change, every group managed to get their signal waveform displayed, though with varying degrees of accuracy. That final day's ordeal really wore us out, but it's a relief it worked out. Both students and teachers look genuinely happy here. Truth be told, this is the only decent photo I have of the signal display. We were so swamped with design fixes that we had neither the time nor the energy to take pictures. I hope they take these back to their schools and actually use them for earthquake observation. We plan to provide after-service support for that purpose. One regret is that we didn't prepare extra weights for the pendulums due to insufficient preparation this time. We intend to include this as part of the after-service support.

These boys also worked really hard. Seeing them so happy with their successful completion made me deeply glad we held this workshop. I sincerely hope they continue observations at their school. What they're showing here is the certificate of participation for this workshop. While not commonly seen in Japanese training programs, these certificates are standard for teacher training here. I hastily signed mine in Roman letters this time and regret not signing in Japanese like I have in the past.

After somehow making it through the three-day workshop, we had dinner at this restaurant tonight. It's a slightly unusual place built over a pond, and once again we savored the mildly spicy Isan cuisine.

At night, I stopped by a DIY shop to replace the hex wrench (which I thought had gone missing during today's workshop → it was actually in my own luggage). But in my haste, I bought an inch-sized one instead of a metric one. I asked them to add it to the STEM room's supplies before moving to Luang Prabang tomorrow. Maybe it was the fatigue from the daytime workshop, but my attention was scattered.

This is the commemorative bag I received during this visit. Plus a tote bag and traditional craft fabric from the local Isan region. I'm deeply touched that they not only hosted me so warmly but also gave me souvenirs.

What made me especially happy this time was receiving an official teacher's uniform. After nearly seven years of coming here, this was my first time getting one. Perhaps they felt sorry for me, as I was the only one in shabby everyday clothes during the workshop opening ceremony where many others were quite formally dressed (sweat). But finally being recognized as a member of this school's staff truly made me very happy.