In spite of being small in area, the weather in Indochina countries are extremely diverse and changeable. At different times, the weather will not be similar. Even at the same time but in two different places, the climate is also differently intense.
Typical example is Thailand, maybe it is dry season in Phuket, but in Koh Samui, 300km away is monsoon season. Therefore, it is important to note that the weather is a very important issue before starting a trip to Indochina.