I want to go to Udonthani from Chiang Mai by bus (VIP or 1st class).

I don't mind stopping for overnights in hotels along the way.

Any suggestions with the bus company names is apprreciated

no stop needed, choice of daytime bus or overnite.

This very same subject has been chewed out here till the very last detail. you do NOT need the name of some comp, which you canot pronounce anyway, you need to know WHICH busstation in Udorn you need to use. But in CM its dead simple: Arcade. lve around 19.30/20.00. be there by 18.30 or so. ask aorund and buy the ticket

no stop needed, choice of daytime bus or overnite.

This very same subject has been chewed out here till the very last detail. you do NOT need the name of some comp, which you canot pronounce anyway, you need to know WHICH busstation in Udorn you need to use. But in CM its dead simple: Arcade. lve around 19.30/20.00. be there by 18.30 or so. ask aorund and buy the ticket

23 hours Chiangmai-Udon? That must be via Bangkok. There is also a bus taking a more direct route.