The street protests began in late October of last year, but the size and level of disruption to the capital city has increased since the start of this year.
"History shows that tourists from China and Hong Kong have been the most sensitive to political turmoil and natural disasters," the note said, adding that this group now accounts for around 20 percent of total visitor arrivals. "Data for December 2013 already showed a collapse in Chinese and Hong Kong visitor arrivals, even before the current political crisis intensified earlier this year."
(Read more: Violent protests expose cracks in Thai economy)
"If political instability lasts for most of this year, the volume of visitors may stay roughly flat in 2014 versus a projection of 7.5 percent year-on-year growth earlier," the bank said in a note.
But Thailand's bane could become a boon for some of its neighbors.
"History suggests Malaysia, and to a lesser extent Indonesia, generally benefit from the substitution effects, while Singapore appears to suffer from complementary effects from a negative tourism shock in Thailand," Credit Suisse said.
(Read more: China tourism boom is 'tip of the iceberg': Hotels.com)
"Thailand and Malaysia's relative tourism growth tend to move in the opposite direction," it said, with Malaysia outperforming the region whenever Thailand's tourism sector experiences negative shocks in most cases. The correlation with Indonesia is slightly lower, it noted.