Nan 740 km. Chao Phraya 370 km. A jacket or sweater may be necessary in the cool season, especially in a mountainous area in the North or Northeast. You have wide range of good buys to choose from. They are beautiful b because Thais are gifted artists, and inexpensive because the labour cost is low.
Sacrilegious acts are punishable by imprisonment even if committed by foreign visitors.
Failing to show respect for the monarchy or making a rude remark about them is an act of less majeste for which the punishment is imprisonment. Even to crease a Thai bank note is an offense as it has an image of HM The King. Generally Thai women are conservative. So don't touch them without their consent. Dress properly when entering a Buddhist temple.