I spent £2000 after 6 weeks in australia not including flights (that would be £3000) so would £3000 be enough? also i’m bacpacking but would like to do hill trekking, rafting and scuba diving once and travel mostly by train or coach

£3000 (excluding air ticket from London, assuming you are from London), should be enough for you to cover all 10 countries in South East Asia (SEA).

All SEA countries (except Singapore) are rather cheap, by western standard.

Conditions: Travel by bus, train in the region wherever possible, overnight in backpaker hostel.