Thailand faces a critical week of court cases that could trigger a political crisis in Southeast Asia's second-largest economy, with the fate of the prime minister and the main opposition hanging in the balance.

Four cases before the courts on Tuesday involve the country's most powerful politicians: Prime Minister Srettha Thavisin, former prime minister Thaksin Shinawatra, the popular opposition Move Forward party and upper-house lawmakers.

For decades, Thailand's politics has been shaped by a struggle between its conservative-royalist establishment, supported by the military, and populist parties such as those backed by Thaksin and the current opposition Move Forward party.