Well, thinking and developing ideas is one thing that separates humans from animals, so when someone says they "cannot think" or they "don't have any idea", they are looking for a quick way out of what is for them an uncomfortable situation ! In some countries in Asia, in Thailand in particular, many people have not been brought up in family or educational circles with a focus on developing their own ideas. You will need to help them learn again ... or rather learn for the first time. Here are three tips I have found to work rather well.
1. Give them some time. Don't stare them down or have them sit in front of you "until an idea comes out". Give them anything from five minutes ("I am going for a break and will be back in five minutes to give you some time to think") to one day ("Let's talk about your ideas again tomorrow at 9 AM"). This releases the pressure of having to come up with something right now or else ....
2. Ask them for three. If you ask for one idea, this is often interpreted as if there is somewhere one correct answer, that you expect them to come up with. This increases the pressure and often blocks people from sharing anything. Asking for three or five sends the message that there is no single perfect answer.
3. Approve right then and there. Experienced managers often have the tendency to take someone's idea or suggestion and modify/improve/complete it. This sends the message that the manager anyway knows better or more. Refrain from this temptation. Approve their idea, or part of their idea, and encourage them to implement it and get back to you in x days to discuss the result. The ownership and learning will be far more powerful.
We all know how to think but sometimes, a bit of help is needed !