how much do you think my itinerary will cost?

i want to overland around most of southeast asia,(not fly) but need an estimate guide as to how much its going to cost me

i will be starting BANGKOK >> SIEM REAP to go to angkor wat >> PHNOM PENH >> SIHANOUKVILLE where I will most likely do water activites >> HO CHI MINH CITY >> NHA TRANG >> HUE >> HANOI >> HALONG BAY >>LOUANGPHROBANG >> VIENTIANE >> CHIANG MAI where i will do the hill tribe trek (3 days) >> BANGKOK

im not sure on my overall time i want to be at these places, but i think a few days in each place is a good estimate, so i would be travelling for roughly at least a month... i also will be budget travelling, and i am a female on my own. i dont want to use any flights either, so either bus or train. roughly how much do you think i will need for this travel route? i am thinking it will be cheap because these are all very cheap places.... also if you have any other places youde like to suggest on my travel route, it would also be appreiciated, thankyou :)