Tobacco companies have targeted Southeast Asia hard, and most countries have high rates of smoking, and accordingly high rates of smoking-related diseases. Local governments have responded with gruesome packaging and bans on smoking on public transport, in offices, and often in restaurants, parks and other public places. Thailand has now banned smoking on major tourist beaches, and the Philippines is debating a ban on smoking in all public places.
Exact rules vary from country to country, but smoking is generally allowed outdoors in the street, but never on public transport. Note that smokers in Singapore also risk falling foul of expensive fines for littering – wherever you are, dispose of butts in a waste bin, not on the ground.