Hi,
Typing “x-400” and “x400” may yield different results, even if you have synonyms enabled – as there is still a possibility for fuzzy/partial matches, where the synonyms does not apply.
There are two ways you can address this. Either by using the keywords exception feature (simply put the dash there). If that does not work, there is a simple programmatical way too.
The programmatical way is probably much better, as it applies to the “raw” prhase, and has a much higher chance of actually working.
I tried to access the actual core wordpress results page on your website, but when I try to go there, nothing is printed: http://kelvinf1.sg-host.com/?s=
If you simply create a custom page, that will not become the results page, wordpress does not work like that. There is a results page handler programmed to your theme, and wordpress triggers that layout whenever the “s” query argument is detected.
If you wish to use that custom page as the “fake” results page, it may still be possible. Try setting the results page redirection to this custom URL:
search-results-page/?asp_s={phrase}
