Thailand is now really becoming a place with a lot of potential. I think we can say that bouldering in Thailand (except from traversing on the beach in the south) really started at Koh Tao, with the dedication of an American guy named James March around the years 2000. Soon followed early 2005 by us, my wife, friends and myself starting developing Sikhiu. With the development of climbing around Chiang Mai there has been some bouldering development as well but the potential is so far not as big as in the central plain and on the Islands. We have had some international visitor such as James Pearson around 2010, his report here (http://www.facebook.com/note.php?note_id=449944482452)
Even the great Chris Sharma came to Thailand but he was led to a less that ideal spot but that is another story....
in 2015/16 Khon Kaen, a fast developing area 6h north east of Bangkok saw the visit of Alex Johnson, Kati Hetrick and Sasha DiGulian who obviously opened some great lines. Some pictures of their visit
The sand stone boulders in Issaan (name given for the North-East Thailand Districts) is spread on a very wide region, from Pak Chong - Sikhiu area up to the Mae Khong river via Chaiyapum and Khon Kaen. Currently Sikhiu and Khon Kaen are really developing however other area have seen climbers such as Chaiyaphum but the potential is huge.