There is an electricity supply of 220 volts throughout Southeast Asia, in the cities and most towns. 240-volt appliances will work safely with this supply. However, there is no universal power point; they vary not just from one country to the next, but from one hotel to another. You can buy adaptors/conversion plugs, from hardware, department and duty free stores, prior to
departure.
In some areas there is a lesser electricity supply of 110 volts, which is available only a few hours each day from the town’s supply or from a diesel generator. Whenever there is limited electricity supply this will also mean limited hot water supply. Remote and village areas also experience power surges or outages, both of which can make re-charging electrical appliances very difficult. We advise you to bring a supply of batteries (bought in Australia/New Zealand) with you to allow for days when you cannot recharge.
Vietnam
Type A (two flat parallel pins) or Type C (two round pins)
Cambodia
Type C (two round pins) or Type G flat three-pin (UK) plug
Laos
Type A (two flat parallel pins)
Thailand
Type A (two flat parallel pins) or Type C (two round pins)
Borneo
Electricity supply is 230V and the plugs are type G (flat three-pin plugs)
Singapore
In Singapore the power plugs are type G (flat three-pin plugs)
Philippines
Source: Electrical Safety First https://www.electricalsafetyfirst.org.uk/