If you have an active AdSense account, go to your account and look for Search Ads as an ad type. I don't know of any separate approval process. You set it up for each site if I recall, but you'll find the details in your AdSense account.

I mean Custom Search Ads, not just Custom Search.

If you search in Google for "AdSense Custom Search Ads" you will find the site. Its not a new product, I think they started this program 2010. I just noticed it some months ago but as I wrote, I did not get any answer yet.

Hope you have an idea.

I see so many simple search websites with this Custom Search Ads.

I can't believe that nobody has a clue here?

Is here someone who is using Custom Search ads?

It's Google CSE. Stands for Google Custom Search Engine. Log in to your google adsense/webmaster account (one login rules them all, right?) and then go back to Google Search and search for: Google CSE. There you'll find how to configure and acquire a search box that can be linked to your AdSense account.

Good luck!

Thank you for your reply.

But I wrote already, I am not talking about CSE.

I am talking about Custom Search Ads.

Therefore I need a active permission.

Ah, ok. Sorry, misunderstood. Does your site fit their criteria?
https://developers.google.com/custom-search-ads/request-permission

If your site is search focused, (for example your users are looking for jobs, travel, products, or local businesses)...

It sounds like it's suited for a low content site, where it's focused on searching for specific products or services. If your site has articles and whatnot then it might not be suitable. Although if they turn you down it would be nice if they send a rejection letter.

Yes, my site is search focused.

But no response actually.

It's a pity because I think it would have a good performance. Should be a perfect match for this product.