Passive constructions
Describe what happens to someone or something with ถูก, โดน and ได้รับ.
Thai can make the person or thing affected by an action the subject. ถูก often introduces an unwelcome event, such as being robbed or bitten. It also has neutral uses, especially in formal and written Thai. Learn these common contexts rather than treating it as an exact replacement for every English passive with be.
The person who acts can be omitted when unknown or unimportant.
My bag was stolen.
The sentence doesn't say who stole it; the agent can be left out.
The thief was arrested by the police.
The agent, ตำรวจ, comes between ถูก and the action จับ.
I was bitten by mosquitoes.
โดน is common in this conversational context; ถูก is also possible.
They were scolded by their mum.
โดน is a more conversational alternative, often used when someone is adversely affected. ได้รับ literally means receive and is common with something received, such as a gift, or in favourable and formal expressions. These are useful tendencies, not a rule that every event must be sorted into good or bad before you can speak.
Three useful choices
An English passive can often become an ordinary Thai action sentence instead. มีคน, someone, supplies an unspecified subject: มีคนชวนผม means someone invited me. This can be more natural than keeping the English passive structure word for word.
I received a gift today.
ได้รับ describes receiving the gift directly.
Someone invited me out for a meal.
มีคน supplies an unspecified person as the subject; no passive marker is needed.
The spelling ถูก has other meanings too. It can mean inexpensive, and ถูกต้อง means correct. Read the surrounding words: before an action it may mark a passive; in a description of a price it may mean cheap.
Common mistake
Don't translate every English was or were with ถูก. For I was invited, consider มีคนชวนผม, someone invited me, or a suitable expression with ได้รับเชิญ. ถูก isn't restricted to harmful events, but the context and level of formality affect which construction fits.
Practise
Kai says
กินข้าว literally means eat rice, but it's also an everyday way to talk about having a meal. A word-for-word translation doesn't always tell the whole story.