The full retail price for that watch (this is the red gold/leather strap PO 600M for anyone who doesn't want to search the ref) is 31k SGD (or 23,300 USD). That's what your local authorized dealer/OB is going to charge unless you can negotiate a small discount.
As for the price difference: I'm not sure what the previous reply-er was saying, but Seamasters, as a rule, do
not retain or increase in value over time, and precious metal Seamasters especially are not great investments. (Watches are not smart investments in general, but if making money on a watch is something that matters to you, Omega is probably the wrong brand. Some models--especially a couple of the Speedmasters--
might do ok, but most of them don't. You can try your luck with the Rolex hype-machine, but it's dicey.) I own a solid gold Seamaster Aqua Terra and was lucky enough to get it for half the retail price in as-new condition. According to a sales associate at one of the largest new- and preowned watch dealers in the world---a Patek and Rolex AD, and a big reseller of Omega---50% retail is the most anyone should ever pay for a precious metal Omega they might someday consider reselling unless they're ok losing a substantial amount of money. There are going to be exceptions to this, but as a general policy, think "half" when considering what your watch will actually be worth on the secondary market.
So... The Japanese dealer may be a gray-market seller who had obtained a brand new watch from Omega at a deeply discounted price and is able to sell it for closer to what it's actually worth. Or it could be a fake watch---always possible.
But if it's one of the Japanese listings on Chrono24 for this piece that I can see right now, there's a different issue. Read the ads on Chrono24 very closely--always. (There's a reason I usually avoid that site almost as completely as I avoid eBay.) The sellers write a good ad, and they even post pictures that make it look like they have the watch in stock. ready to sell to you at that wonderful price. But if you pay careful attention, you'll see that they say the "
Item needs to be procured," or "
Item available on request." They do
not have these watches ready to sell. Chrono24 should help to ensure that you don't get swindled, but your money could be tied up for a long time, and you could be waiting weeks or months only to find out that no watch is available at that price after all.
As best I can tell, the only legit Chrono24 listing for that piece is in Germany, for 24k SGD, and I'm not sure they'll ship to Singapore...