Hi, i'd like to add my two cents and share experience and do not have intention to ofend any one
Was in Bangkok two years ago and returned in my lugages few bettas and shrimps
Was walking through "chatuchak" market in the animal district ( I highly recomend a visit of this area in chatuchak, Amazing place despite animals are not well taken care off, saddly,
you will find in this market, litteraly any thing flying, walking, swimming, crawling... that south east Asia can have ! you wana reptiles, insects, cats, dogs, fishes, birds... it has and plenty. very interesting walking around)
anyway, i ended up in front of a shop with beautiful bettas, best breeds ever! they were a little pricey due to the fact of special breed, but you can also find some bettas as cheap as 5 thai baht (same ones you find at your LFS)
i couldn't resist buying 3 of them for their beauty, thinking how would i bring them back with me? while walking further I ended up in an air condition shop selling breeds of shrimps, again i couldn't resist buying 20 of them
back to the hotel I transfered my bettas in 50 cl bottles of water keeping the water that shops provided me, i didn't sealed the bottles yet, just comtemplating my purchase
the transport in lugages : 1/4 water and 3/4 air per bottle, one bettas is each, before leaving hotel for the final trip i closed my bottles and put them carefuly between my shirts
back home, i saw straight away that my lugages have been open by the Thai customs as a little sticker was put on my locker, i though that they didn't pass the customs but my surprise when opening has been that all botlles were here and intact and that all fishes and shrimps actually survived
i do not invite anyone doing it, just sharing. last trip i did in Thailand few months ago i did not bring back with me any fishes.
cheers