Pattaya check out
www.apexhotelpattaya.com this is a cheap girl friendly hotel not stayed there myself but have heard good reports.
When i was in Pattaya last september I stayed in the nautical Inn 700 bht a night on beach road Soi 11.
Phuket (patong) i think i will be staying either at
www.patongvilla.com or
www.harrys-phuket.com both i hear are good and and girl friendly.
Sorry do not know about bangkok or samui