I want to take issue with the idea that Bali is a "side trip" from Thailand. First of all, BKK-DPS is a 4-hour flight. Secondly, Bali alone is a one-weeker type of destination; it's hardly worthwhile to blow in and out for a couple of days or so. And with only 2 weeks total, what's the point of splitting it 3 ways?

Suggest that this trip be rethought and limit the side trip to Cambodia only. If they want to save some coin and add dimension to the side trip, I suggest they fly BKK-PNH spend a day or so, then road trip to Siem Reap which will take a few hours. Then road trip SR back to Bangkok (about 7 hour) or fly one-way from REP-BKK and hold their nose at the cost.