If the OP - or anyone else - is still interested, try:
Pattrara Prepress.
242/2 Manee Nopparat Rd.
Sri Phum, A. Muang. Tel. 053 210 816
Located near Chang Puak Gate, it's the go-to place for graphic arts professionals in Chiang Mai.
If you can't get what you want there, it's Bloom Pro Lab in Bangkok.
They will accept and return work by mail or courier.
Not cheap but numero uno for quality prints in Thailand.