Does anyone have any suggestions on how to get more traffic from keywords?
this can be achieved by creating high quality content that fully addresses the intent of the keyword.
I just looked at your site (the English version only), and I saw a lot of weird / poor sentences. It looks like the entire content on your site is auto-generated, and that's NOT high quality.
There are a lot of misspellings, internal links thrown in randomly (this is particularly bad because google - and your visitors too actually - are interested only in links that are relevant to the topic of the article and which flow naturally into the content, but some of your internal links just pop in there without rhyme or reason)...
There are also sentences that are not finished.... and there is also no period between sentences, the last word of the previous sentence is glued to the first word of the next sentence.
Now, I don't know if the plugin you're using does a poor translation from Thai to English and / or messes up the structure of the sentences, or if the original article (which I assume is written in Thai) is poorly written / constructed, but you do need to improve the quality of your content. Otherwise I don't think you'll get much ranking / traffic...
And also the internal links, don't forget to work on those too because - like I said - at the moment, many internal links are not flowing naturally into the content. They are still related to the content, yes. But they just pop in there without logic, and that's not good
How can I create more diverse keywords?
1) put the main keyword(s) into google and scroll down to the bottom of the page and see what other keywords / topics google suggests. Sometimes, some of those suggestions are great for easy rankings and traffic.
But don't limit yourself to the first suggestions of those main keyword(s) only! Click on those suggestions and scroll down again to the bottom of the page and see what other suggestions pop up. Do this few times and you can get pretty good long tail keywords (which is what I assume you mean by "diverse") that could work out well...
2) as
@iAuthority said, plop your main keyword(s) into tools like Ahrefs or Semrush (you can find pro accounts for Semrush in the marketplace that are heavily discounted if you can't afford buying directly from Semrush's website) and see what similar / related keywords these tools show. For some niches, you can get literally 1000s of good keywords that could work well for your case.
3) create a google alert for the main topics / keywords of your site to receive updates on what people look for, or what new is being said / written by the media / other sites
4) use reddit.com to find out what people are wanting / asking for in your industry.
@Steptoe has shared a great method to uncover quality keywords using Reddit, so use this method!
https://www.blackhatworld.com/seo/guide-keyword-research-via-reddit.1577914/
5) take the top 3-5 competitors ranking in google in your industry / niche, plop their websites into Ahrefs / Semrush, and check which pages they get ton of traffic for, for keywords that they don't target, and then you can target those keywords to (hopefully) get some of that traffic too
PS: and yes, don't make your sites, niches and keywords public on SEO forums, you never know who's going to steal your easy niches and keywords