Actually Tim, this is not correct on both counts.
The Japanese can only land on the east side of Malaya, the British Dutch contol the Sea of Malacca. Japan really only has solid control along the Thai coast on the Gulf of Siam.
After taking some serious losses at the Kota Bharu landing on Dec 8, the Japanese wouldn't attempt another landing, despite having two more planned with troops sitting in transports in Indochina.
The Japanese 55 infantry regiment (of the 18th division) was supposed to land at Kunatan at the end of December, but the Japanese air force had failed to neutralize the defending RAF, so it was unable to land. Unlike the quick establishment of air superiority in the Philippines, the RAF maintained operations in Malaya during Dec Jan.
Instead of the planned landing the 55th also had to sail to Kota Bharu, and elements of the 18th division spent 3 weeks hiking through the jungle (along the coast) to attack Kuantan.
The 114th regiment was supposed to land at Mersing to drive into the British flank and cut them off. During a Japanese conference on Jan 11 (when they captured Kuala Lumpur) the Japanese air force had still been unable to eliminate the RAF, so the landing was cancelled.
Actually not true either, the Japanese can only blocade Singapore if they gain control of the airfields in Southern Johore. The British were able to bring in resupply convoys and over a dozen ships without interference. They managed to sink the CPR Empress of Asia, (and prevent further supply) which only occurred on Feb 5, 1942. (All the previous ships had gotten through).
The last British troops had retreated onto Singapore island on the 31st of January, abandoning all of Johore (and the airfields there) to the Japanese. As long as the British halt the Japanese advance in northern Malaya and have enough aircraft to deny Japan air superiority, they can continue to supply Malaya
Freebird, thanks for the response. I'm not sold on the viability of it as it, taken as a whole, leads to the Dominion forces not losing the Penisula and Singapore. But they did. While many of your points have validity, one has to accept the history is what it is.
For instance, while the RAF was not absolutely, positively wiped out, it was no longer a viable force. The difference between Air Supremicy and Air Superiority. All the Japanese needed as Superiority. That, they attained. Later in the war, when it was the Allies turn to take ground, the same situation occured. For instance, in the Phillipines during 1944, the Japanese still aircraft operating but they were not a major factor. Nor was the RAF in Singapore after the first couple of weeks of the war. They were just worn down to the point of being an annoyance and not much of a threat.
As for the blockade, it is rare that a blockade is 100% effective. Something always gets in and out. Especially in the early parts of a blockade. The longer they last, the more effective they become. Singapore never got to that level.
As for negating the effect of having command of the seas, I agree with your premise that the Japanese never did another serious invasion after Khota (the invasion of Singapore Island notwithstanding), but they really didn't have to. The collapse on the penisula was so complete, that they got where they wanted to go on land. If the situation had been different, they could have used that command of the sea to go where they wanted and do as they wished. It never came to that, but the option, if needed to be used, was available.