The oldest taxis I saw were some late 1980s Ford Lasers, although the vast majority of taxis were from about the last seven or eight years.

The most common taxis, from my memory:

Toyota Corolla Altis
Mitsubishi Lancer (locally built, they have a different trunk design)
Nissan Sentra (locally built by Yulon)
Nissan Teana
Toyota Camry
Toyota Corona Premio
Ford Tierra