On the morning of 20 May the Thai Army Chief proclaim martial law across the whole of Thailand. In that respect is increased military presence in Bangkok and neighboring states with some roadblocks.
You should leave additional time for journeys, including to the Bangkok airports.
Political confirmation continue in and around Bangkok and elsewhere in Thailand. Some of these have been violent, including the use of firearms and grenades, and there have been casualties and deaths. The position is irregular and further protests are expected.
You should avoid protest sites.
Protest action in central Bangkok since January 2014 has caused significant disruption to roads in affected regions, with knock-on effects across the metropolis.
The main protest site is at Ratchadamnoen Avenue with a smaller protest site at the government complex at Chaeng Watthana. On that point are also sporadic rallies to government agencies and private societies.
There have been aimless attacks involving weapons and explosives at protest sites and at protest marches. The attempts have taken home during the daytime and at nighttime.
You should get special care and avoid all protests, political gatherings, demonstrations and marches. Monitor local news and social media for spread.