In case someone will need it one day.
Hopefully these several lines below will save you a lot of your precious time in searching for a place to make a stamp in Thailand.
So, if you need to make a rubber stamp then you should go to the next spots:
Bangkok: shopping mall MBK, the 1st, 3rd or 4th floor. I haven’t been there but people say that they did rubber stamps there withing couple of house and just for 150 Bath.
Samui: it’s getting harder if you need a stamp on this island. It’s easy to find in the Internet that the stamp could be made at Samui Aksorn (Thaweeratphakdee Road, Nathon 103/1 Moo 5, Tambon Angthong Koh Samui, Suratthani, 84140 Thailand; Tel: 0 7742 0192-3 , 0 7742 0707, 0 7742 6036 , 0 7742 6159 Website). But I could not find it driving there and back along the road over there, moreover nobody answered to my phone calls. But website is working and updated… So, might be I just searched not good enough.
Another place to make a rubber stamp at Koh Samui is a small printing shop across the road from Sea View Hotel in Nathon. It’s closed on Sundays. They asked for 500 Bath and promised to make it withing 2 days but I didn’t like the price, so left without a stamp.
Krabi: printing center (white and red building) next to the post office building (coordinates: (8° 3’39.18″N, 98°55’6.91″E), just type it in Google maps — and ta daaam!). They made a stamp for me withing 24 hours and it coasted me 200 Bath. Paint for the stamps could be bought in the shop across the road and a bit forward (in the direction of the post office) for 30 Bath. They also print stuff from USB-drivers at once for 5 Bath/page (black and white) and 10 Bath – for color printing.
In case you know about places where it’s possible to make a rubber stamp in Thailand which are not mentioned here – I would be glad if you share this information!