There are two different issues in your question:
- Whether you can import and use a drone in a foreign country.
- What the rules are for lithium batteries on flights.
Some countries do not allow drones at all, or require specific permits or licenses to import or use them. I'm not going to cover this aspect here, but you should definitely check that. The Drones and Model Aircraft Stach Exchange is probably a better place to ask.
Regarding batteries, the IATA guidelines for passengers regarding lithium batteries tells us that you are allowed to carry up to 20 spare batteries.
- Must have a capacity under 100 Wh.
- Must be in your carry-on luggage, not in your checked luggage.
- Need to be properly protected and isolated.
If the battery does not show the capacity in Wh, you can derive it from the capacity in mAh or Ah. Multiply by 3.7 V to get mWh or Wh. Divide by 1000 to convert mWh to Wh.
So a 2000 mAh battery is 2000 * 3.7 = 7400 mWh = 7.4 Wh.
The largest battery you can carry is about 27 000 mAh.