You can! This is because FOAM Map uses what’s called partial-lock voting. Voters never lose their tokens. When you vote, your voting credit is only partially-locked.
The ‘partial’ part means you can and should use the same tokens to vote in multiple challenges at the same time.
The ‘locked’ part mean that once you submit your vote, the voting credit is not withdrawable until you:
Reveal your vote during the Vote Reveal phase.
or unlock the voting credit under the Voting tab of My Assets after the Vote Reveal phase has concluded.
NOTE: You're not allowed to submit additional votes to the same challenge if you have already submitted some.