When travelling, it's generally smart to pack in preparation for rain or any other conditions that may arise. The rainfall in Bangkok Intl is roughly similar to Timisoara. You can assume this to be the case over the next 3 days.
Expect the weather to be around 36 °C on average in April. As the temperature peaks, try to get your plans done early, as flight price and availability will have an impact on your travels. The climate in Timisoara is generally colder than in Bangkok Intl.