Baltic States have practically nothing. Yet they claim to be living in fear of Russia!
If they are so scared of that, why don't they all get large armies and bring in military service?

Belarus on the other hand seems to have a really large military. Who/what are they afraid of..?
These are rather simple questions, IMHO. Baltic States are NATO members with collective defense system, and it's now mainly the US responsibility to protect them in the event of any aggression, in accordance with the charter of the organization. So they can save up a little bit of cash for other more pragmatic purposes that can give a return in the future. It's as simple as that. As for Belarus, they are basically afraid of the USA and NATO. It’s crucial for most dictators to instill the belief that enemies abound and ready to attack at any moment. That feeling of external aggression allows them to make the population more loyal and obedient to the dictator and ready to bear the brunt of current economic and political hardships with less complaint, because there is a good reason for it.