Thailand is 11 days into the (largely?) nonviolent attempt to overthrow the current government. The government opponents escalated the conflict with an attempt to take over the Police HQ and various airports. They continue the occupation of the prime minister's office building.
The government reacted by attempting to arrest 9 protest leaders, and tried to evict the protesters from government buildings.
The prime minister said that he would not use force, but, after supporters of his party (which has support largely from the rural areas) attacked the protesters. The BBC quote is "when a screaming crowd of government supporters – armed with sticks and slingshots – ploughed into a group from the PAD". Street clashes resulted and the PM called a state of emergency in Bangkok.
The military doesn't seem eager to get involved with police staying on the sidelines during clashes or attempting to keep the two sides apart. I haven't had time to look up other sources than the BBC, so it is possible that the military and police are using harsher methods with government supporters since the military overthrew the previous government by the PM's party.
The foreign minister has left the government and the PM has called for a referendum that will "ask a range of questions including whether the
government should resign, whether it should dissolve parliament and
what people thought about the ongoing protests." (BBC) The protest leaders opposed it, though considering that they don't want an elected parliament, it doesn't seem that surprising.
The BBC has pictures from the latest clashes.