When your kid says they no longer want to wear a diaper it can usually mean that the kid is ready to potty train.
Some kids will just let you know that they want to stop wearing diapers and are ready to use the toilet.
If your kid suddenly tells you they no longer want to wear a diaper then take that as a good thing if they are old enough to use the toilet.
Remove the diaper and then tell them that if they no longer want to wear a diaper then they have to go pee and poop in the toilet.
If they refuse to use the toilet and pee and poop in their underwear then it's back to diapers until they can go on the toilet.
Some kids may tell you they no longer want to wear diapers even when they are not ready to use the toilet so it doesn't always mean they are ready to use the toilet.
But sometimes it is.
If the child is removing their diaper and not using the toilet then you can use masking tape on their diaper or duct tape around their diaper to keep it on them.
Some kids just hate wearing diapers even though they must wear them and in that case you have to force the child to keep the diaper on.