In this day and age it’s possible to travel around the world – from Ushuaia to Ulaan Baatar – and speak nothing but English the whole time.
Why bother learning Thai or Hindi, when touts in Bangkok and Delhi can hook you up with everything you could possibly want or need – “Very Cheap, My Friend, Special for You!”
The answer, of course, is that making the effort to speak a few words of the local language will lead to a more authentic, fulfilling, unique and memorable travel experience.