Many people come to Thailand just for seeking mindfulness therapy. Here are some places we would recommend.

Suan Mokkh International Dhamma Hermitage (SMIDH), part of Wat Suan Mokkhaphalaram in Chaiya, Surat Thani province
Web site: www.suanmokkh-idh.org

Wat Ram Poeng, Chiang Mai
Web site: www.watrampoeng.net

Wat Phra That Doi Suthep, Chiang Mai
Web site: www.fivethousandyears.org/center

Wat Phra That Chom Thong, Chiang Mai
Web site: www.sirimangalo.org

Wat Pa Sunan (Wat Sunandavanaram), Sai Yok District, Kanchanburi province
Web site: www.watsunan.org

House of Dhamma
Web site: www.houseofdhamma.com

Dhamma Kamala Thailand Vipassana Centre
Vipassana meditation courses in the tradition of late Burmese meditation master Sayagyi U Ba Khin of Burma (Myanmar)
http://www.kamala.dhamma.org/
http://www.dhamma.org/

Vipassana Meditation Courses in Thailand
http://www.dhamma.org/en/bycountry/ap/th.shtml

(sources from TAT E-Magazine)

If you want to learn more about meditation, please visit http://www.tourismthailand.org/meditation