Customs and Duty for Tourists visiting Thailand - personal items and food supplements

Hello,

I've been searching through the forums but am still not sure about customs regulations for tourists entering Thailand (i.e. for a temporary stay). Apologies if this seems really stupidly obvious - but any help would be much appreciated.

I intend to travel to Thailand next week just for a short trip, carrying just basic stuff (clothes, personal possessions etc).

My question is, would I have to declare any of my own personal items? My phone alone is worth much more than the allowances amount of 10,000 that is specified on the Thailand Customs Department website. I don't intend to bring anything new and boxed into the country - just my clothes, phone laptop etc etc.

Now...I know.... it sounds stupid...I'm 90% sure you can enter a country with a mobile phone and a laptop without having to pay for the the privilege....but I've never been anywhere like Thailand before and thought I had better check! I assume people must walk through there with iphones and the like all of the time - but again I just don't know as I have never done it.

Related to this, I was also considering bringing some bodybuilding supplements with me (new and sealed), probably just some whey protein, maybe a pre-workout supplement. I'm erring on the side of not doing this though, in case it causes issues at customs. Do I need a licence or permit or something to allow me to bring in something as basic as protein powder? I don't want to land myself in a cell just for trying to bring some of my creature comforts with me!

Any help very kindly appreciated, regards