Are the only things that matter to you safety and cost? Is there anything in particular you enjoy more like exploring nature, beaches, cities, etc? Is there anything that you need like strong infrastructure, reliable wifi, little risk of extreme weather patterns? This list can be extensive without some fine tuning. However, if the only things that matter are safety and cost, Ho Chi Minh City in Vietnam is probably your best bet. It’s likely one of the cheapest options as far as marrying COL with a relatively modern city. It def has its issues but it’s safe and extremely affordable.