Hey Louise,
Looks like you are in for an awesome adventure. Are you limited by time at all e.g. returning for work? I would say 3 weeks thailand , 3 weeks in vietnam and 1 week in Laos just sticking to Luang Prabang, vang Vieng and Vietiane (I have linked to each itinerary with a city breakdown). However I understand that not everyone can spend that long away from home.
If you are limited by time I can highly recommend booking a G Adventures as I have done a few trips with them recently. They are fast paced and more expensive than you would typically spend backpacking. However they tick off all the highlights and its a great introduction to backpacking (especially their 18-30 something trips).

I’m currently planning my Asia trip from the UK and wanted to ask how long is good for each place in Thailand? I’m new to backpacking so
Will mix up hostel and hotels and will
Try to fly where possible. I’m just trying to plan my flights and don’t want to miss out by not giving myself the right amount of time in each city. Thank you :)

Ps I’m aiming to do Thailand/Vietnam and Laos.

Hey Cay!
Glad you found this article helpful!