Southeast Asia forum

Depending on what you want to do - with just a month you could easily fill your time From Vientiane to Chiang Mai with trips out to the Plain of Jars and Mung Ngoi and some hiking in Lam Nan Tha (bring a fleece that way as it can get chilly in the evening) - and with a friend living somewhere that is when you have the best advantage of a place and would be well served with a whole week just stationed there in Chiang Mai to really absorb the place, that's what I did a few years back and did not regret it.

However, if you really want to see Cambodia, the issue is that you need at minimum a week to make it worth while for a detour, at least Siem Reap and PP. You could just dip into Siem Reap if that is what you mean by not wanting to miss Cambodia and catch a flight up to Vientiane if you're willing to garner the expense (or out of PP for that matter and then just speed up your trip through northern Laos) . . because otherwise you are rushing through Southern Laos's wonders just to get up to the north. . . you won't be able to spend much time in 4,000 Islands, Champasak, Pakse and the Bolavan Plateau - to say nothing of Savanakhet.

It is probably better to choose Cambodia and a flight to Vientiane with a quick loop through Luang Prabang-Luang Nam Tha and into northern Thailand OR going directly to Vientiane to take time exploring northern Laos more thoroughly.