Bangkok is the capital of Thailand. Frankfurt has flights to Bangkok, direct or with a stop. Abbasi Travels can search flights for you.
It is hot all year. The coolest and driest months are roughly November to February. The rainy season is roughly May to October. Figures and seasons differ between sources, so treat this as a rough guide.
Whether you need a visa depends on your passport and on how long you stay. Open our visa check to see what we have researched, and always confirm on the official government website before you book.