The 3.05 million tourists in June spent about 150 billion baht ($4.86 billion), up 1.48pc from a year earlier.
Visitors from China, Thailand's biggest source of tourists, declined 7.1pc in June from a year earlier, after falling 8.55pc in May.
Preliminary ministry data this month showed a fall of 4pc on the year in June overall tourist arrivals.
Foreign tourist receipts make up about 12pc of Thailand's gross domestic product.