Those who love wild bettas will likely associate Bung Khong Long Lake, located in Bung Khang Province in northeastern Thailand, with the guitar-shaped Betta smaragdina.
I myself first visited Bung Khong Long Lake to collect and research guitars.

When I first visited Bung Khong Long Lake, it was larger than I had imagined. In some places, it was labeled as "○○ Beach" in English, and it really did look like a swimming beach.

As we drove along the lakeshore, we saw small fishing boats here and there, and near the shore, we could see fish farms that looked like they were raising some kind of fish.
Ton struck up a conversation with a fisherman who had just finished fishing and was returning.
Unlike me, who is shy around strangers, Ton is not afraid to talk to anyone and quickly becomes friends with them.
This is a big difference from the Japanese; even strangers can chat for an hour or more.
This could be considered a talent; thanks to this personality, he can quickly make friends with locals wherever we go and gather information. He's a reliable partner.

When I spoke to a fisherman who had returned after finishing his fishing, he said he had caught small shrimp, a specialty of this lake. These shrimp appear to be a species closely related to the Japanese freshwater shrimp.
The net-covered fish farms in the shallow waters near the shore are apparently where these small shrimp are kept.
As I was being shown it, I noticed that there were dead pufferfish scattered all over the place.
This freshwater pufferfish, formerly known as Pao palustris, was once imported into Japan, but is currently unavailable as it is on Thailand's export ban list.

When I spoke to the fishermen, I understood why this pufferfish was found dead around the shrimp tank.
Pufferfish, which love small shrimp, are said to come to the tank to steal and eat the shrimp.
Therefore, fishermen reportedly kill them on sight.
Since exports were not prohibited at the time, Ton told the fishermen that he wanted these pufferfish to ship to Japan, and they told him he could take as many as he wanted.
Of course, if fishermen can get someone to buy the harmful fish that steal and eat their goods, that would be a godsend for them.

I fondly remember visiting the fisherman the next day and finding that he had gathered the pufferfish for me. I packed them in oxygen and brought them back to Bangkok.
In the fall of 2025, on my way back from Laos, I visited this fisherman at Bung Khong Long Lake for the first time in a while.
Bung Khong Long Lake was completely transformed into a resort, bearing almost no resemblance to its former self, but the famous shrimp fishing industry was still thriving.

Just then, one of the fishermen who had been out fishing returned and was spreading out his nets on the boat, sorting through his catch.
This fisherman's net is truly a treasure chest, teeming with various kinds of fish that inhabit Lake Bunkonglong, along with small shrimp.

This time, the most noticeable fish in the net, along with the Pao Palstris, was a marbled goby.
I don't recall seeing this species much before, so I put it in a plastic bag I had on hand to examine it, and it turned out to be a very fascinating species.
For the time being, I gathered only the individuals that seemed to be in good condition from the net, packed them up, and took them back to the inn.
I asked the fishermen to gather up any fish they caught the next day, promising to buy them, but my request was not granted.
Well, I suppose not many people would take a request from an outsider seriously, so I'm not too disappointed, as this is nothing new.
Looking at the gobies I had packed, I realized they were the same species as the yellow gobies that had been caught in my net along with guitarfish and golden chalery when I was collecting them in a place called Seka.

The one I collected previously was still a juvenile and had a different body color, so I couldn't recognize it as the same species, but it's almost certainly the same.
I asked an acquaintance who is knowledgeable about freshwater fish in Thailand, and he quickly told me that this goby has the scientific name Neodontobutis aurarmus, is closely related to the Japanese goby (Donko), and is a species endemic to the Mekong River system.
It seems to have English names such as Mekong Sleeper and Golden Arm Sleeper, but I'd like to call it Golden Arm Sleeper here.
I thought the individuals I picked up from the net at that time would fall off because they were quite worn, but they all showed incredible vitality and recovered without dying.
Despite their appearance, they seem to be a hardy species, and in fact, they were easy to keep.

When I observed the two fish I brought back to Japan in my home aquarium, I noticed that while they normally have a predominantly yellowish body color, when the two of them meet, their body color darkens, transforming into a very attractive marbled pattern.
However, they don't engage in fierce fights, so even if multiple individuals are kept together, their fins and other parts don't seem to get damaged.
They prefer live food, but they readily accept frozen bloodworms, making them easy to keep.
When kept as a pet, they will show signs of coming to the corner of the tank when they see a person, making them very cute and suitable as pets.
I hope that in the near future, Ton will go to Lake Bung Khong Long to collect these Golden Arm Sleepers and ship them to Japan.

Personally, I would love to go back to Bung Khong Long Lake to collect specimens and take photographs at a leisurely pace, and try their famous tempura-style kakiage (mixed vegetable tempura) made with small shrimp.